1. Field of the Invention
This invention relates generally to air admittance valves for plumbing systems and more particularly to a one-way valve designed to allow air to enter the plumbing drainage system when a pressure less than atmospheric pressure develops.
2. Description of Related Art
Individual and branch-type air admittance valves for sanitary drainage systems are devices used as vent terminals in plumbing drainage systems. These valves are not used to relieve backpressure, but to allow air to enter the system when even a slight negative internal pressure occurs. When the valve of the type of the present invention is installed in a building, at least one open vent terminal which extends to atmosphere outside of the building serves the same building drain on which these valves are installed. Therefore, the valves are designed to be used for individual fixtures or for a branch serving multiple fixtures.
Typical plumbing systems introduce water and carry away waste, the water being supplied under pressure to the plumbing fixtures and drain pipes carry waste and water from the fixtures to a drain emptying into sewer systems or septic tanks or the like. Atmospheric pressure is maintained in the system and gases are vented by vent pipes that open to the outside. Plumbing fixtures typically contain a trap which holds water to prevent gases from entering the building through the fixture. Such venting allows air to enter the system to prevent a vacuum from forming. Common procedure in building plumbing systems is to utilize roof vent pipes for providing air when negative pressures are realized in drain plumbing systems.
Related air vent valves include U.S. Pat. No. 6,234,198 to Chalich which teaches a combined vacuum relief and pressure containing valve assembly for relieving vacuum in conduits, while also serving as a check valve preventing elevated pressures from propelling fluids past the valve. Beckey, et al. teaches a one-way flow valve assembly comprised of a valve body having an internal valve chamber in communication with the ambient environment with a valve seat. The primary object of Beckey's U.S. Pat. No. 6,415,816 patent provides for an automatic air admittance valve which permits ambient air under ambient pressure to enter and equalize a negative pressure differential in a plumbing drain, while preventing the discharge of gases under positive pressure conditions.
In U.S. Pat. No. 5,419,366, Johnston teaches a valve assembly for automatic venting of excess negative pressure in a drain line. An elastomeric diaphragm is drawn against a valve plate having a passageway therethrough which is normally closed by the diaphragm and, at a predetermined differential pressure across the diaphragm, causes the diaphragm to lift away from the plate to open the passageway.
There is a need in the industry for a valve containing a movable diaphragm which quickly and reliably seats and seals air flow when closed and allows air to enter when open. The valve of the present invention includes a housing which contains a movable free-floating diaphragm which seats and seals air flow when closed and allows outside or ambient air to enter when open.